A prior art insulating-liquid immersed inductor comprises, as shown in Japanese Patent Unexamined Publication No. 63-241909, an inductor body including an iron core and a coil, and a hermetically sealed tank in which the inductor body is arranged, non-flammable insulating liquid fills a part of a space between the inductor body and the hermetically sealed tank to immerse the inductor body therein, and the other part of the space is filled by pressurized insulating gas. A part of the pressurized insulating gas is absorbed in the non-flammable insulating liquid so that the volume of the pressurized insulating gas decreases in the tank. In the prior art insulating-liquid immersed inductor, when the pressure in the hermetically sealed tank is decreased according to the decrease of temperature in the tank, the absorbed insulating gas returns to gas, so that the insulating liquid includes many bubbles therein. The bubbles of the insulating gas cause the insulating strength to decrease in the inductor, because the insulating strength of the insulating gas is lower than that of the insulating liquid between the coated wires of the inductor.